Green nanotechnology against toxic cadmium: Mechanisms, progress, and the path to future solutions

Cadmium (Cd²⁺) contamination remains a critical environmental and public health challenge due to its high mobility, persistence, and severe toxicological effects, including oxidative stress, enzymatic inhibition, and organ bioaccumulation. Nanoadsorbents derived from sustainable resources have emerged as promising candidates for water remediation, offering high efficiency, tunable surface chemistry, and environmental compatibility. Despite significant progress, critical gaps remain unaddressed. In particular, the mechanisms governing regeneration stability of green nano-adsorbents are still poorly understood, which restricts their translation to large-scale applications. Moreover, systematic cross-comparisons of adsorption capacity, selectivity, and stability across material classes are limited, and existing reviews rarely establish a direct link between cadmium’s molecular toxicity mechanisms and adsorbent design strategies. To address these gaps, this review provides a mechanistic synthesis of advances in inorganic-nanoadsorbents including clay minerals, biomass-derived carbons, chitosan, agricultural waste-based nanomaterials, and green-synthesised metal oxide composites and evaluates how physicochemical factors such as surface area, porosity, functional group density, adsorption kinetics, and thermodynamics govern Cd²⁺ binding. A distinctive contribution of this work is the integration of cadmium’s toxicity pathways with the rational design of adsorbents, while also highlighting emerging domains such as biodegradable nanomaterials and AI-assisted material screening. By identifying unresolved challenges in scalability, regeneration, and long-term stability, this review not only deepens mechanistic understanding but also outlines practical technical pathways for developing next-generation, sustainable, and environmentally safe technologies for cadmium remediation.